1. Field of Invention
The present invention relates to a method for manufacturing semiconductor devices, and particularly relates to mounting semiconductor chips on tape substrates.
2. Description of Related Art
In the field of semiconductor devices, TCP (Tape Carrier package) is well-known as a type of package with bear chips mounted. This involves a semiconductor chip being mounted on a film tape carrier 30 shown in FIG. 4. The film tape carrier 30 is normally formed by applying copper foil on a polyimide resin film, forming a circuit thereupon, and then applying Sn plating or Au plating, and is formed as a long article before being worked as a semiconductor device. Leads are formed of inner leads 20 connected to bumps formed of Au or the like on electrode pads on the semiconductor chip, and outer leads 36 formed integrally with the inner leads 20 and extended for external connections.
The following is a description of a TCP manufacturing method using gang bonding wherein all bumps and inner leads are simultaneously connected. First, on a stage not shown in the drawings, a semiconductor chip is positioned at a location surrounded by device holes 32, and positioning is performed so that each of the bumps on the semiconductor device and the inner leads to be connected thereto are properly connected. This positioning is performed using two of the bumps and inner leads on a diagonal line, out of the bumps and inner leads at the four corners. Next, as shown in FIG. 5(A), A heating tool 50 heated to around 500xc2x0 C. beforehand is lowered to the positioned bumps of the semiconductor chip 40 and the inner leads 20. The heating tool 50 lowered on the inner leads 20 applies pressure so as to press the bumps and inner leads 20 against the stage.
Further, in the event that the bumps are formed of Au, for example, an Au/Sn eutectic alloy 46 shown in FIG. 5(B) is formed of the Sn plating of the inner leads 20 and the Au, due to the heat applied from the heating tool. Following connection of the bumps and the inner leads 20 by this eutectic alloy 46, a resin of epoxy or the like is applied by dropping or printing and then hardened (not shown) in order to avoid mechanical stress and ensure humidity resistance, thereby completing mounting of the semiconductor chip 40 onto the film tape carrier 30. After the semiconductor chip is mounted, the film tape carrier 30 is punched, thereby removing the unnecessary portions of the film tape carrier 30. The above steps complete the TCP.
In the event of connecting the bumps of the semiconductor chip and the inner leads using a heating tool as described above, there have been the following problems in actual practice.
That is, there is a difference between the linear expansions coefficients of the semiconductor chip and the film of the film tape carrier. As described above, the film of the film tape carrier is formed of polyimide, so the linear expansions coefficient of the film is greater, and the pitch of the inner leads becomes longer. Accordingly, in the event that the bumps and inner leads are formed with the same pitch at the stage before thermocompression bonding thereof with the heading tool, there will be difference in the pitch of these by the time that the heating tool comes into contact with the inner leads.
Accordingly, as shown in FIG. 6, even in the event that part of the bumps and inner leads are correctly connected as with the bump 10C and the inner lead 20C, there is positional shifting between the two at other places. In extreme cases, the shifting may be to the extent that proper connecting is difficult, as with the bump 10D and the inner lead 20D. This shifting occurs due to the heat of the heating tool as described above, and thus can be avoided by increasing the descending speed of the heating tool immediately before thermocompression bonding. However, increasing the descending speed of the heating tool leads to applying shock to the semiconductor chip which causes damage, thereby lowering the reliability of the manufactured semiconductor device.
Accordingly, it is an object of the present invention to provide a method for manufacturing a semiconductor device wherein both bumps of the semiconductor chip and leads on the tape substrate can be accurately connected at the time of performing thermocompression bonding of the two using a heating tool.
According to an exemplary embodiment of the present invention, a manufacturing method for a semiconductor device, wherein a semiconductor chip is mounted on a tape substrate, includes a step for causing leads formed on the tape substrate and bumps formed on an active face of the semiconductor chip to face one another; and a step for lowering a heating tool and bringing this into contact with the leads, and performing thermocompression bonding of the leads and the bumps.
In this exemplary embodiment, the lowering speed of the heating tool is changed up to coming into contact with the leads.
With this exemplary embodiment of the present invention thus configured, changing the lowering speed of the heating tool allows the time of contact between the leads and heating tool to be controlled, thereby suppressing stretching of the tape substrate due to heating to a minimum.
Also, with the above semiconductor device, the lowering speed of the heating tool has been made to decrease as the leads are approached.
With this exemplary embodiment of the present invention thus configured, the lowering speed of the heating tool is set to be relative to fast at first, thereby reducing the time of contact between the leads and the heating tool, so that stretching of the tape substrate due to heating can be suppressed to a minimum, and also the lowering speed of the heating tool has been made to decrease as the leads are approached, so as to not apply shock at the time of the leads coming into contact with the semiconductor chip to a degree of damaging the semiconductor chip.
Also, the speed of the heating tool may decrease to approximately 5 mm/second immediately before coming into contact with the leads.
Further, the heating tool is preferably lowered from above the leads at a speed of around 50 mm/second for example, and at the point of descending to a height of 0.1 to 0.5 mm from the leads, the subsequent descending speed is changed to around 5 mm/second.
Also, the tape substrate which is used may have the pitch of the leads set 0.01 to 0.03% shorter than the pitch of the bumps.
With this exemplary embodiment of the present invention thus configured, the difference in the linear expansions coefficients of the tape substrate and the semiconductor chip has been taken into consideration, in the event of using polyimide tape substrates in particular, and accordingly the pitch of the leads has been set 0.01 to 0.03% shorter than the pitch of the bumps, so the pitch of the leads and bumps can be made equal immediately prior to the thermocompression bonding.
Also, the temperature of the heating tool may be set to approximately 520xc2x0 C., and thermocompression bonding of the bumps and the leads is performed.
With this exemplary embodiment of the present invention thus configured, the temperature of the heating tool is a temperature minimally necessary for suitably forming the eutectic alloy between the bumps and leads, thereby suppressing stretching of the tape substrate.
Also, according to another exemplary embodiment of the present invention, a semiconductor device manufacturing method for bonding a tape substrate, upon which leads are formed, and a semiconductor chip, upon which bumps are formed, on an active face thereof includes at least a step for preparing the tape substrate such that the pitch width of the leads has been set beforehand so as to be equal to a value obtained by multiplying the pitch of the bumps by the ratio of the linear expansion coefficient of the semiconductor chip as to the linear expansion coefficient of the tape substrate at the heating temperature of thermocompression bonding of the bumps and the leads; a step for positioning at least one reference bump of the arrayed bumps and a reference lead to correspond to the reference bump such that the center lines of the reference bump and the reference lead overlap, and also for positioning each of the leads so as to face respective the bumps; and a step for lowering a heating tool from above the leads and bringing this into contact with the leads, and performing thermocompression bonding of the leads and the bumps.
Also, according to another exemplary embodiment of the present invention, a semiconductor device manufacturing method for bonding a tape substrate, upon which leads are formed, and a semiconductor chip, upon which bumps are formed, on an active face thereof includes a step for preparing the tape substrate such that the pitch width of the leads has been set beforehand so as to be equal to a value obtained by multiplying the pitch of the bumps by the ratio of the linear expansion coefficient of the semiconductor chip as to the linear expansion coefficient of the tape substrate at the heating temperature of thermocompression bonding of the bumps and the leads; a step for positioning at least one reference bump of the arrayed bumps and a reference lead to correspond to the reference bump such that the center lines of the reference bump and the reference lead overlap, and also for positioning each of the leads so as to face respective the bumps; and a step for lowering a heating tool from above the leads and bringing this into contact with the leads, and performing thermocompression bonding of the leads and the bumps.
According to this exemplary embodiment, the lowering speed of the heating tool changes as the leads are approached.
With this exemplary embodiment of the present invention thus configured, the thermal expansion between the tape substrate and semiconductor chip at the time of thermocompression bonding of the leads and the bumps has been taken into consideration beforehand for the pitch of the leads, so the pitch of the leads and bumps can be made equal immediately prior to the thermocompression bonding. Thus, the bumps and leads can be connected properly. Also, positioning of the tape substrate and semiconductor chip is performed such that the center lines of a reference bump situated at approximately the center of a row of bumps and a reference lead situated at approximately the center of a row of leads overlap, so at the time of lowering the heating tool from above the leads and bringing it close to the bumps and leads, even in the event that unexpected shifting of pitch occurs between these, the shifting of the bumps at the end of the bump row and the leads at the end of the lead row which are situated farthest from the reference bump and reference lead, can be minimized.
Also, changing the lowering speed of said heating tool may allow the contact time between the leads and heating tool to be controlled, thereby suppressing stretching of the tape substrate due to heating to a minimum.